In paved road construction, it is common practice to establish a compacted roadbed using a scraper blade to scrape the road bed surface at a proper roadbed depth. Procedurally, the compacted roadbeds are typically prepared from a rock base comprised of gravel or stone which must then be leveled and compacted to the appropriate height before paving with a suitable top surface such as concrete or blacktop which typically mates onto the gutter of the curbstone. Within recent years, there have been developed sonic and laser tracking devices which attach to a road grader. These tracking devices typically include a transducer which generates laser beams or sound pulses which enables the tracking device to measure the roadbed depth and control the grade with physical reference to base lines such as a curbline surface, a string line, or other existing road surface landmarks. This provides an appropriate road bed for laying the concrete, black top or other surfaces onto the road bed. These sonic or laser tracking devices are designed to include software and hardware which automatically adjusts the grader moldboard to the appropriate grading height so as to provide the proper rock bed grade prior to the laying of the finished road bed surface. Exemplary of such sonic or laser devices which measure and control the roadbed grading elevation are referenced in an owner's manual entitled the BLADE-PRO™ Motorgrader Control System, copyrighted 1992, Spectra-Physics Laserplane, 5475 Kellenburger Road, Dayton, Ohio, and an operator's manual entitled Motorgrader System Five™ by TOPCAN Laser Systems, Inc., 5758 W. Las Positas Blvd, Pleasanton, Calif. 94588, both of which are incorporated herein by reference.
In order to prepare a suitable road bed for paving, the finished rock bed grade must be within ¼ inch tolerance so as to meet mandated road building engineering specifications. This will normally require a number of passes before the roadbed meets the required specifications. A major problem with such sonic and laser measuring devices is the fact that the monitoring measurement relies upon the perceived curbstone flag or gutter surface as a guideline to control the elevation of the moldboard. Unfortunately, if, in fact, there exists any debris from past grader passes upon the curbstone gutter surface (e.g. such as gravel) then the automated reading for positioning the grading moldboard will become grossly distorted. The sensing device will react to the more elevated debris resting along the targeted beam line causing the moldboard to be inaccurately raised to an inaccurate grading elevation. Accordingly, the perceived evaluation of the curb control line becomes distorted by whatever debris may be resting upon the curbstone gutter surface. It is customary to initially manually sweep graded materials from the curbstone flagging so as to permit the sonic or laser measuring devices to record an accurate measurement of the actual distance between the rockbed and the curb flagging edge. Conventional grading moldboards will accordingly inherently sweep excessive or unwanted material onto the curbstone flagging or gutter. This in turn distorts the true curbline depth resulting in automatic adjustment of the moldboard to an excessive amount of road bed abutting onto the curbstone and places the road bed in non-compliance with road building specifications. The need to constantly sweep graded debris from the curbstone flagging increases the costs, manpower, equipment and time needed to complete a roadway project. The advantage of a grader moldboard regulated by an automatic sensing device can be readily frustrated by an inability to maintain the targeted beam line in condition for an accurate reading. There also exists a need to more accurately control the amount of material cut or graded along the leading edge of the moldboard as well as being able to more accurately and more uniformly control the distribution of graded material along the trailing edge of the moldboard. The ability to effectively limit graded spill and unwanted debris at a moldboard grading edge would significantly enhance the efficacy of moldboard grading.
The present invention provides an attachment which alleviates the problems attendant to the conventional use of the grading moldboard. The present attachment serves as a moldboard attachment to accurately cut and grade the roadbed while maintaining and preventing accumulation of debris onto the curb or work site. The attachment provides a more uniform and accurate distribution of graded material. This allows the sonic or laser measuring device to provide an accurate and more uniform control of the moldboard in a grading operation.